Investigating the effect of morphological, qualitative and yield traits in order to identify the most promising cotton genotypes in Hashemabad, Gorgan

Background and objectives: Despite the new varieties of cotton that have been improved, introduced and marketed in recent years thanks to the efforts of cotton breeders, increasing the genetic diversity of the country's gene bank and introducing new varieties with higher yield, earlier maturity and better fiber quality. This study was conducted to evaluate the agronomic and quality traits of cotton varieties bred using different breeding methods that have shown their superiority over commercial varieties in one or more traits in Hashem-abad region of Gorgan. This research was conducted to determine the effectiveness of the measured traits of cotton genotypes.
Materials and methods: In this study, 5 genotypes 90-10481, 92-34, 92-48, Va-1, and Va-2 were compared along with controls Golestan and Varamin in the form of a randomized complete block design with three replicates in 2018-2019 by using the combined analysis method and principal components analysis with GTBiplot graphical analysis and selecting the best genotypes.
 Results: Based on the results of combined analysis of height traits, number of sympodial branches, number of bolls, percentage of earliness, yield (30 bolls, first picking, second picking) and total yield, fiber yield (30 bolls), of seed weight (30 bolls and first picking), fiber length, uniformity, fiber fineness, firmness, fiber elasticity, total percent lint, and percent lint of 30 bolls were significant at the 1% statistical level when genotypes were examined. According to the obtained results, four components had a higher root than two (5.88, 5.27, 3.12 and 2.05). The first four components explained 90.65% of the total changes between the data. In the first component with a value of 32.65, early maturity and weight of 30 bolls traits, in the second component number of bolls and total yield, in the third component fiber length and strength traits, and in the fourth component fiber elongation and fineness traits and percent lint explained the changes. The greatest variation shown by the biplot diagram in genotypes Va-1 and VA -2 in traits related to yield included total yield, number of bolls, yield at first picking, yield at first picking, and earliness. VA -genotypes Va-1 and VA -2 are positively correlated with each other and negatively correlated with genotypes 92-48, 90-10481 and 92-34 and Golestan cultivars. VA -1 genotype has a zero correlation with the varamine variety, since they have an angle of about 90 degrees. Therefore, VA -1 genotype and Varamin variety have different genetic background that causes their differences.
 Conclusion: The results show that the Va-1 and Va-2 genotypes are capable of introducing new varieties and can also be used in breeding programs to create greater genetic diversity. In addition to their high yield, they were earlier than the other genotypes studied. Genotype Va-1 proved to be an early maturing genotype with high uniformity of fiber and high yield at the first harvest. Genotype Va-1 had the highest yield among the studied genotypes with a high number of bolls and sympodial branches. These traits can be taken into account in breeding programs to improve commercial varieties and to produce new varieties.